1. Field of the Invention
This invention relates generally to programmable interconnection arrays and more particularly to an optical waveguide cross-connect array with programmable connections.
2. Description of the Related Art
Long-range signal communication over optical fiber is gradually displacing the more traditional electronic or radio-wave transmission. Originally, optical fibers were used mainly for high-density, long-haul applications in which electrical signals representing data were used to modulate a laser at one end of the fiber. The light received at the other end of the fiber was detected and converted to an electrical signal in the detection process. Such a process avoided switching an optical signal between selected fibers because the electrical signals derived from the optical signals could be switched conventionally and then reconverted to optical form for a long-range retransmission on another fiber. However, modern optical fiber signal transfer is also applied to numerous medium and short haul communication links and efficiency now demands extensive optical cross-connect switching for signal routing. A switching matrix that uses bubble manipulation in a liquid to control signal paths has yielded very positive results but long-term reliability has not been verified for large-scale bubble switching matrices. Other types of optical switches are commercially available, but suffer from one or more of cost efficiency, unwieldy size, poor performance, or a known lack of long-term reliability.
Similarly, the local transfer of signals to and from an integrated signal processing device such as an integrated circuit (IC) is usually accomplished by electrical means. Because of the physical limitations of both the circuitry and the signal transfer media, the very high speed communication devices expected in the near future must use optical signaling and interconnections for acceptable information transfer efficiency. A typical means for high-performance local electrical signal transfer and interconnection is the modern high-density printed circuit board (PCB). In a PCB, the electrical signals are routed on thin conductors, separated laterally and vertically by an insulating dielectric. Photolithographic techniques are used to render the pattern of conductors on each layer, and the layers are laminated to form a three-dimensional electrical interconnection array. Interconnections between vertically separated layers are added to ensure maximum interconnection density.
Optical equivalents of the modern high-density PCB are not known in the art. In particular, the manufacture of high-density customized interconnections using optical waveguides is widely believed to be difficult and impractical. What is needed is an apparatus and procedure to provide a programmable set of interconnected optical paths on a substrate suitable for the cost-effective implementation of customized optical interconnections for local signal transfer. The related unresolved problems and deficiencies are clearly felt in the art and are solved by this invention in the manner described below.
This invention solves the optical interconnection efficiency problem by providing a mass-produced substrate containing a network of intersecting optical waveguides in which a permanent cavity may be created at any one or more intersections to permanently cross-connect the two intersecting waveguides, thereby producing a permanent custom optical interconnection.
The present invention provides a process for mass-producing devices embodying a network of intersecting waveguides in which cross-connections between selected waveguide pairs can be permanently programmed at low cost using automated equipment. It is a feature and an advantage of this invention that programmable optical substrates providing customized local connectivity between a plurality of optical components may be efficiently and reliably fabricated.
one aspect, the invention is a process for fabricating an optical waveguide cross-connection array, including the steps of preparing a supporting substrate, forming one or more first waveguides fixed to the supporting substrate, forming one or more second waveguides fixed to the supporting substrate and disposed to form one or more intersections with the first waveguides, selecting at least one intersection to be switched, and changing the optical parameters at the selected intersection, whereby the optical signal entering the selected waveguide intersection from a first waveguide is redirected to exit the selected waveguide intersection by way of the second waveguide.
In another aspect, the invention is a method for programming, according to an interconnection map, an optical waveguide cross-connection array having a plurality of waveguides fixed to a supporting substrate to form one or more waveguide intersections, including the steps of selecting at least one waveguide intersection to be switched according to the interconnection map, and creating a permanent cavity having a second refractive index in the waveguide material of the selected waveguide intersection, whereby the optical signal entering the selected intersection from the first waveguide is deflected by the cavity to exit the selected intersection by way of the second waveguide.
In an exemplary embodiment, the invention is a programmable optical waveguide cross-connection array including a supporting substrate, one or more first waveguides fixed to the supporting substrate, one or more second waveguides fixed to the supporting substrate and disposed to form one or more intersections with the first waveguides, and a cavity in at least one of the intersections at least partially empty of all material other than gas, whereby the optical signal entering the at least one intersection from a first waveguide is redirected by the cavity to exit by way of the second waveguide.
The programmable optical waveguide cross-connection array of this invention for the first time provides an optical equivalent of the modern high-density PCB featuring a high-density customized interconnections using optical waveguides that is relatively inexpensive and easy to manufacture while providing the necessary reliability required for modern optical networks. Programming of individual arrays can be automated and is permanently fixed in the array so that the array of this invention for the first time provides a low-cost mass-produced device featuring permanent customized optical interconnections for local signal transfer.